1. Field of the Invention
The present invention relates to liquid crystal display (LCD) devices, and in particular to LCD devices with continuous insulation wall structures.
2. Description of the Related Art
Liquid crystal display (LCD) devices have many advantages such as small volume, light weight and low power consumption, and are applicable in a variety of electronic and communication devices including notebook computers, personal digital assistants (PDA), mobile phones and the like. From a fabrication point of view, LCD devices formed by one drop filling (ODF) methods can reduce liquid crystal fill time, and have therefore become main stream methods for fabricating LCD devices.
FIG. 1 is a cross section of a conventional liquid crystal display device. A liquid crystal display device 100 includes a first substrate 10, a second substrate 50, and a liquid crystal layer 70 interposed therebetween. The LCD device 100 further includes a plurality of pixel regions P defined by the intersection of gate lines (not shown) and data lines 26. Each pixel region P comprises a region with an active device T such as a thin film transistor (TFT) and a pixel electrode 32. The thin film transistor comprises a gate 12 electrically connecting the gate line (not shown), a semiconductor layer 20 formed on the gate 12, a source 22 formed on the semiconductor layer 20 connecting the data line 26 and separating from drain 24 by a specific distance.
A first insulation layer 14 and a second insulation layer 28 are formed over the first substrate 10. A black matrix (BM) 52 is formed over the inner surface of the second substrate 50 opposing the first substrate 10. The black matrix 52 is positioned corresponding to the region with active devices T, gate line (not shown), and scan line 26.
The second substrate 50 further comprises color filters 54 on the black matrix 52. The color filters 54 can be further divided into three color regions such as red (R) 54a, green (G) 54b, and blue (B) 54c. Each color region is positioned corresponding to a pixel region P. A passivation layer 56 and a transparent common electrode 58 are sequentially formed over the inner surface of the second substrate 50. Both the first substrate 10 and second substrate 50 comprise an alignment layer over the inner surface. Spacers 60 are disposed in the liquid crystal layer to maintain a gap between the opposing substrates.
In general, a typical LCD device requires two parallel substrates with a highly precise gap therebetween. Two substrates 10 and 50 are aligned and assembled with a cavity therebetween. Next, liquid crystal 70 is filled into the cavity by vacuum injection, and the cavity is sealed, completing large scale panel devices using vacuum injection, however, is inefficient and lengthy.
In order to improve liquid crystal injection efficiency, a method of one drop filling (ODF) is proposed. After a frame is formed on a flange of a substrate, liquid crystal is directly dripped in the frame region of the substrate. An opposing substrate is subsequently assembled on the substrate. The ODF method, however, usually results in inadequate or excessive liquid crystal being filled, thereby leading to irregular display (mura defects). Moreover, when a large scale TFT-LCD is set upright, distribution of the liquid crystal becomes unbalanced due to gravity causing mura defects. A novel LCD structure is thus required to prevent unbalanced LC distribution and ameliorate mura defects.
U.S. Publication No. 2004/0263766, the entirety of which is hereby incorporated by reference, discloses a liquid crystal display device as shown in FIG. 2. In FIG. 2, each red (R), green (G) and blue (B) pixel is surrounded by a continuous protruding wall 108 to serve as spacers. Spacers can prevent unbalanced liquid crystal due to gravity. The continuous protruding wall 108 is disposed on the black matrix 102. The continuous protruding wall 108, however, may cause isolation of liquid crystal between adjacent pixel regions, and cause further assembly difficulties.